The term "post combustion" is also known in the art as "after-burning". Therefore, these terms will be used interchangeably in this application.
A known method for post combustion of combustible components in the atmosphere in steel smelting vessels includes, feeding a jet of oxygen through an oxygen lance into the working space of the steel smelting unit (vessel) above the level of the metal in the vessel. In this method, the oxygen is fed through an apparatus having several rows of outlets in the form of jets which are aimed in a direction which is inclined with respect to the horizontal plane. The outlets are positioned at different levels in the vessel or furnace.
The apparatus includes an oxygen lance in the form of concentric pipes for the introduction of oxygen into the vessel, and for providing cooling water for the apparatus. At the discharge end of the lance apparatus and extending along its length, blowholes are positioned for the oxygen, in the form of jets, to exit the lance. Such a device is shown by E. D. Merker in his publication "Gas Dynamic Protection of the Blasting Zone in Steel Smelting Installations," Moscow, Metallurgiya, 1994, at page 20, FIG. 5.
A disadvantage of using the known device is the low efficiency seen in both the process of post combustion (after-burning) of the gases evolving in the steel smelting unit and in the creation of a gas dynamic curtain.
Due to the fact that the jets are discrete entities, the necessary intermixing of the furnace atmosphere with the oxygen jets does not take place. Moreover, when the known method and device are used, the heat evolving during the after-burning of the combustible components is not returned to the molten metal. The discrete feeding of oxygen in separate jets does not create a continuous gas dynamic curtain over the metal bath. Under these conditions the efficiency of after-burning of the combustible components will not exceed 50-60%.
U.S. Pat. Nos. 5,050,848 and 5,051,127 disclose an apparatus and method for post combustion over a molten bath using a swirling gas flow by means of one or more tuyeres directed at the surface of the metal.
U.S. Pat. No. 5,166,950 discloses a process for post combustion (after-burning) in a metallurgical furnace.
European Patent Publication 0 544 044 A1 discloses another post combustion process.